Beta-HCG Level

Sample for Beta-HCG Level

1. This test is done on the serum or urine of the patient.
2. Can save serum at 2 to 8 °C for  24 hours for total HCG.
3. For more time, keep serum at -20 °C.
4. Freshly voided urine first-morning sample is preferred and centrifuge at 900 x g for 10 minutes.
   • Can store urine at 2 to 8 °C for 48 hours.
5. β- HCG serum is stable for 7 days at 2 to 8 °C. For longer periods, freeze it at -20 °C.

Indications for Beta-HCG Level

1. To diagnose the pregnancy.
2. To monitor the high-risk pregnancy.
3. Diagnose ectopic pregnancy.
4. Screening of Down syndrome.
5. Used as a tumor marker.
6. HCG level is also used to monitor the therapy and progress of the disease.
7. This can be used as a marker for placental and germ cell tumors.

Precautions for Beta-HCG Level

1. Negative tests if done in the early stage of pregnancy. This is a false-negative result.
2. Avoid a sample of hematuria and proteinuria which gives the false-positive test.
3. Hemolysis in the urine gives the wrong result.
4. Maybe negative in the diluted urine, so a morning sample is preferred because it is concentrated urine.
5. Taking a history of drug use, like diuretics and promethazine, may give a false-negative result.
6. Drugs like anticonvulsants, tranquilizers, and hypnotics give a false-positive result.
7. Radioisotope administered in the last week may affect the result.

Pathophysiology of Beta-HCG Level

1. The HCG is a glycoprotein with a molecular weight of 37,900 D higher carbohydrate portion as compared to other hormones,  and it is made of two subunits:
   1. Alpha (α).
   2. Beta (β).
2. The HCG is produced by the placental syncytiotrophoblastic cells.
3. Chromosome 6 codes for the α-subunit, and Chromosome 19 codes for the β-subunit.
   1. The peak of the β-HCG is 6 to 8 weeks.
   2. While α-HCG keeps on increasing.
   3. HCG stimulates the corpus luteum, which produces progesterone in the first week of pregnancy.
   4. Progesterone:
      1. Prevents menses.
      2. It supports pregnancy.

4. The α- subunit is the same for all the glycoproteins, Like LH, FSH, and TSH, while the β-unit is unique for HCG.
   1.  Molecular weight is around 14,900, with 10,200 for protein and 4700 for carbohydrate.

β-subunit (Beta HCG) level

1. The β-subunit is specific for HCG.
2. The molecular weight of the β-subunit is 23,000 for proteins, 16,000, and 700 for carbohydrates.
3. The ratio of α-subunit to β-subunit increases two-fold between the first and third trimesters.
4. The HCG and its β-subunit can detect early pregnancy, which is present in the blood and urine. This is excreted by the kidneys.
5. β-HCG sensitivity can detect pregnancy as early as 6 to 10 days after the oocyte implantation.
   1. The amount is the same in the urine and serum by one month.

HCG (HUman chorionic gonadotropin)

1. HCG will appear in the pregnancy as early as 10 days after conception and is found in the serum and urine.
2. HCG  plays an important role in maintaining the functions of the corpus luteum during the first week of pregnancy until the luteoplacental shift of progesterone production has occurred.
3. HCG also promotes steroidogenesis in the fetoplacental unit and plays an important role in stimulating the fetal testicular secretion of testosterone.
4. The human fetal testes have specific binding sites for HCG.
5. The maximum level of fetal testosterone in the fetus occurs around the peak level of HCG secretion during the pregnancy.
6. In the first few weeks of pregnancy, its level rises where the serum level is higher than the urine level.
7. This blood test detects beta-HCG (human chorionic gonadotropin), a hormone normally produced during pregnancy and in some cancers.
8. The intact molecule of HCG is more specific for pregnancy.

9. After delivery, the HCG level falls rapidly in the first 2 to 3 days and is undetectable after 2 weeks.
10. The persistence level of HCG means trophoblastic disease. It needs the workup of the patient.

HCG was detected by the following methods (Pregnancy tests):

1. Biological method where the urine was injected into a rabbit (1920). Now it is obsolete.
2. An immunological method like agglutination inhibition test (AIT).
   1. β-HCG is a better test to detect pregnancy after 18 days of conception in the urine.
   2. After the monoclonal antibody, the detection of the pregnancy improved, and now pregnancy can be detected 3 to 7 days after conception.

3. Radioimmunoassay (RIA).
   1. This is reliable and sensitive to detect the β-HCG subunit of HCG.
   2. The best sample is the blood for RIA, but urine can also be used.
   3. RIA can detect pregnancy before the first missed cycle.
   1. Radioreceptor assay (RRA).
      1. This test is done on the serum and is very sensitive and accurate.
      2. 90% to 95% positive after 6 to 8 days of conception.
      3. This test is very useful if someone wants to terminate the pregnancy; also good for the infertile couple anxious for the confirmation of pregnancy.
      4. This can detect the minute amount of HCG secreted in the ectopic pregnancy.
      5. This test is helpful in monitoring spontaneous abortion.
4. Home test kits are based on the immunometric or immunochromatographic technique.
   1. The detection limit is 50 IU/L.
   2. Their clinical specificity is 77% to 100%.
   3. While their clinical sensitivity is 31% to 100%.
   4. The high number of false-negative results is difficult to understand in the literature.
5. False-positive 1% results in urine are due to the following:
   1. Protein.
   2. Drugs.
   3. Bacteria.
   4. RBCs.
   5. White blood cells.
6. False-negative results occur because the test usually does not detect levels at a concentration of less than 25 to 50 IU/L.
   1. 1. Cold reagents, high temperatures, and extreme pH give a false result.

If serum HCG is positive (raised):

1. If there is no pregnancy, it means the placenta is not properly implanted in the uterus, then it may indicate:
2. 1. Ectopic pregnancy.
   2. Miscarriage.
   3. Testicular cancer.
   4. Trophoblastic Tumor.
   5. Hydatidiform mole.
   6. Ovarian cancer.
3. If the urine test is negative but clinically indicates pregnancy, then repeat the test within 1 to 2 days.
   1. A urine test may be negative when the serum is positive for HCG.

The normal level of HCG and Beta-HCG

Source 2

• Qualitative test = negative (positive in pregnancy)
• Men = < 5.0 mIU/mL
• Non Pregnant women = < 5.0 mIU/ mL
• another reference
  • normal = <2 ng/mL
• Urine = > 25 mIU/ ml suggests pregnancy.
• β- HCG normal value = <2 ng/mL

Source 4

• Men = <5.0 mIU/mL.
• Nonpregnant women = <5.0 mIU/mL.
• Pregnant women: